据花粉分析试论郑州大河村遗址的地质时代和形成环境

本文通过对郑州市大河村遗址沉积进行系统的孢粉分析,结果表明,遗址沉积时期的大部分时间,为距今5740一4410年,气候暖和润湿,气温较今稍高,其时植被面貌属森林草原类型或森林类型。遗址沉积物的地质时代属第四纪的全新世     

新疆罗布泊罗4井的孢粉组合及其意义

本文应用孢粉分析,对罗布泊罗4井沉积的地质时代和古环境进行了探讨。指出:沉积物堆积期间的气候下部干凉,上部温干,植被属荒漠类型,沉积物的地质时代为晚更新世至全新世。 罗布泊是我国最大的咸水湖,也是我国和世界上最为干燥的地区之一。为了探讨它的成因,恢复其地史时期的自然面貌,本文系统地研究了罗4井的孢粉,现就孢粉分析结果进行一些讨论     

花粉浓缩物的加速器~(14)C年代测定初探

在环境敏感带的风积物、湖积物剖面中采集了 1 7个样品 ,建立了适用于风积物中花粉浓缩物提取的实验方法 .将花粉浓缩物的测年结果与某些已知年代样品作了对比研究 ,进行了花粉浓缩物的加速器14 C测年的初步探索 .结果表明 ,在稳定环境下与沉积物同时沉积的花粉测年具有一定的可信度 .它将为改善黄土高原晚更新世以来年代测定提供一条新的可能途径 .同时 ,将14 C测年与野外地质观察相结合 ,提取了该敏感带晚更新世向早全新世转换过程中 4次主要的季风降水变化的地质记录     

岷江上游堰塞湖沉积中软沉积物变形构造成因讨论

对在岷江上游及其支流河谷中的晚第四纪古堰塞湖地层中发现的大量软沉积物变形构造的类型、特征和成因进行了分析,发现这些软沉积物变形构造分为两类:一类是小型的层内变形构造,如液化卷曲变形、泄水构造、负荷构造、阶梯状微断裂等,其形成与软沉积物的塑性变形、液化和流动作用相关;另一类是崩(滑)塌体对软沉积物的扰动形成的大型褶曲构造.通过与其它成因的软沉积物变形构造的对比以及对区域构造环境的分析,得出地震、崩塌和滑坡等灾害性地质事件是造成河谷区古堰塞湖地层中软沉积物变形构造发育的最可能的驱动机制.     

应用古文化层埋深确定汾渭盆地沉积速率的研究

根据４９处仰绍至东周古化遗址深数据 距今７０００－２５００年汾渭盆地内部的沉积人部的凸起地区沉一般小于凹陷地区,如渭河凹平均沉积速率为０．４６ｍｍ／ａ临当凹陷的平均沉积速率为０．３６ｍｍ／ａ,而潼凸起和襄汾凸起的沉积速率为０．２０ｍｍ／ａ左右,分析各时代的沉积速率还发现,在仰绍之前渭河盆地内凹陷的沉积速率明显小于 仰绍之后,宝鸡凸起还由东周之前的相对下降变为相对上升,沉速度相对较大的地质单元往往     

吉林榆树周家油坊晚更新世孢粉组合及其意义

本文是对吉林榆树周家油坊二级阶地沉积进行孢粉分析的总结。从孢粉资料可以说明,沉积物堆积时期的古植被属森林草原类型,气候寒冷较湿。通过孢粉组合对比,二级阶地形成的时代为晚更新世晚期。 周家油坊在吉林省榆树县西南18公里,因该处二级阶地盛产第四纪哺乳动物化石,所以该地不仅成为东北地区第四纪的“标准”地层之一,也尝有“榆树动物群”之称。但因化石层位欠清,所以在地质时代等问题上仍存争议。为了探讨“榆树动物群”的生活环境及阶地沉积的地质时代,建立该区第四纪孢粉地层层序,在二级阶地采集了一些样品进行孢粉分析     

中国南海北部陆架区更新世晚期沉积物年代学及古环境研究 ——以DG钻孔为例

大陆架作为海陆相互作用的关键地区,对于研究大陆的构造演化、海陆变迁、海平面升降以及气候变化具有重要意义.然而由于不同研究方法的局限性,目前对大陆架沉积物年代学及其蕴含地质信息的认识仍然不足.南海是西太平洋最大的边缘海,是全球海洋沉积作用最为活跃的地区之一,也是海陆相互作用最为典型的区域.作为东亚大陆物质的主要沉积区,南海已经受到了学术界越来越多的关注.然而,目前的研究工作主要集中于沉积连续、信号记录稳定但沉积速率较慢、总体分辨率较低的深海区沉积物.相对而言,沉积速率较快、分辨率较高的浅海大陆架沉积为高分辨率年代学和古环境的研究提供了重要的地质材料,但由于大陆架沉积环境动荡导致沉积信号记录不稳定甚至缺失.针对南海大陆架沉积,尤其是对钻孔沉积物高分辨率年代学研究仍相对较少,限制了对南海构造与气候演化过程的认识.为了更好地限定南海北部陆架区更新世晚期沉积物的年代,研究其中蕴含的古环境信息,探讨东亚地区气候变化的驱动机制问题,同时为南海海域活动构造研究提供年代学框架,文中以南海北部DG钻孔为研究对象,在微体古生物化石和碳同位素年龄(14C)数据的基础上,利用大陆架沉积物磁化率与深海氧同位素的对比对其沉积物年代学进行了系统研究.基于此,结合色度和孢粉结果,对其古气候意义进行了初步探讨.结果表明,该钻孔沉积物的磁化率可对应于深海氧同位素的阶段1—阶段9(MIS 1—MIS 9),底部年龄约为300ka,磁化率低值区间对应于冰期,高值区间对应于间冰期.这与该钻孔沉积物中的孢粉和色度所记录的古环境信息相吻合.冰期时气候较为寒冷,水体变浅,沉积物搬运距离相对增大,矿物以氧化作用为主,主要形成弱磁性的磁性矿物(如赤铁矿),导致磁化率较低;间冰期时,气候相对暖湿,水体变深,沉积物搬运距离相对缩短,矿物以还原作用为主,主要形成强磁性的磁性矿物(如磁铁矿等),导致沉积物的磁化率显著增强.因此,南海大陆架北部更新世晚期沉积物的磁化率变化可以反映东亚地区更新世晚期以来冰期—间冰期气候旋回.磁化率与深海氧同位素的对比作为一种晚第四纪松散沉积物的相对定年方法,在南海北部陆架区更新世晚期沉积物定年方面是适用且可靠的,可为海洋大陆架沉积物定年和对比研究提供新的参考.     

应用古文化层埋深确定汾渭盆地沉积速率的研究

根据４９处仰绍至东周古文化遗址埋深数据研究了距今７０００～２５００年汾渭盆地内部的沉积速率．结果表明,盆地内部的凸起地区沉积速率一般小于凹陷地区,如渭河凹陷的平均沉积速率为０．４６ｍｍ／ａ,临汾凹陷的平均沉积速率为０．３６ｍｍ／ａ,而临潼凸起和襄汾凸起的沉积速率为０．２０ｍｍ／ａ左右．分析各时代的沉积速率还发现,在仰绍（距今５０００年）之前渭河盆地内凹陷的沉积速率明显小于仰绍之后,宝鸡凸起还由东周之前的相对下降变为相对上升．沉积速率相对较大的地质单元往往是地震活跃的地区．     

地震振动液化形变的研究

多种地质作用可造成年青的松散沉积物发生变形。为了判别沉积形变中的地震振动液化形变形迹,着重讨论了振动液化形成机制、形变几何形态特征以及它们与融冻变形和准同生变形构造的区别。认为振动液化形变形迹可以作为鉴别古地震标志之一。     

从孢粉分析试论北京地区两泥炭矿的时代和形成环境

本文应用孢粉分析,对北京地区两个泥炭矿的时代和形成环境进行了探讨。指出:泥炭成矿时期的气候是温暖而湿润的,气温较现今高。植物生长茂盛,属针阔叶林植被。泥炭是在植物残体的不断积累、分解和腐烂,长期保存在水体及后期泥砂覆盖的还原环境之下,上覆压力不断增加,沉积物的堆积速度与湖沼下降的速度长期保持相对平衡等条件下形成的。泥炭成矿的地质时代主要在中全新世     

Rock magnetic properties of Nihewan sediments at Xujiayao

Rock magnetic measurements of Nihewan sediments from Xujiayao section demonstrate that magnetite, hematite and maghemite are dominant remanent magnetization carriers. Monitoring the variations of magnetic susceptibility (MS) and saturating isothermal remanent magnetization (SIRM) at low temperature are the attractive ways of detecting the presence of magnetite, maghemitization and superparamagnetic grain sizes. Low-temperature MS investigations suggest that susceptibility enhancement for Xujiayao samples is mainly due to the remarkable presence of SD/MD magnetite to some degree though some magnetite grains have been partially oxidized at some depths. It is tentatively concluded that both SD/MD magnetite and hematite are of detrital origin and carry a characteristic remanent magnetization (ChRM), whereas maghemite can be attributed to be chemical origin, overprinting a reversed polarity component of Matuyama age.     

新疆富蕴地区晚第四纪松散沉积的孢粉研究

据对新疆富蕴吐尔洪及干沟等剖面的孢粉分析,揭示这些剖面沉积时期的气候温和干燥,植被为荒漠草原或稀树草原。孢粉分析结果及14C年龄数据说明,这些沉积物的地质时代属全新世。通过对取自断层两侧沉积物的孢粉分析研究,获知此断层的形成时间不会早于全新世     

A~200 ka pollen record from Okinawa Trough:Paleoenvironment reconstruction of glacial-interglacial cycles

Pollen analysis was carried out on the Core MD982194 of 29.78 m retrieved from the Middle Okinawa Trough which was dated as old as~200 ka BP.The results revealed that pollen assemblages mainly presented an alternation of coniferous and herb pollen.The coniferous saccate pollen,principally Pinus and Tsuga,predominated in most parts of the core,especially highlighted in the interstadial stages including MIS 1,3,5 and MIS7,whereas the herb pollen significantly increased in the glacial periods.Thus the pollen flora and their percentages showed the sensitive changes under the influence of ice volume during the glacial and interglacial periods.Our record from this core has first documented that the percentage of Cyperaceae was extremely high in the glacial stages with a notable increase in Artemisia,Gramineae,Asteraceae,Chenopodiaceae,and freshwater algae,which can be used as a proxy for sea-level change at the study site because of their close negative correlation of the orbital-scale changes in sea level.The distance between the continental coastline and the Okinawa Trough has deeply shortened due to the sea-level drop in the LGM.As a result,the sediment materials from Yangtze River were extensively deposited on the flat,exposed continental shelf owing to the rapid decline of river flow speed,leading to that pollen grains from Okinawa Trough are derived mainly from the flat coastal vegetation of exposed continental shelf at glacial stages.Changes of pollen assemblage were consistent with the variation of temperature and humidity,which showed that the percentage of arboreal pollen was highly augmented at MIS 7,5 and MIS 1,corresponding to the strengthening of the East Asian summer monsoon and increasing of rainfall.Moreover,the peak of Pinus percentage in MIS 5.3,5.1 and MIS 3.3 may be closely linked by orbital and sub-orbital cycles of solar radiation and monsoonal variability.The present study of core MD981294 implied lower temperature and precipitation during the lowest sea-level stage(LGM),and more visibly testified that the vegetation of the flat plain on the exposed continental shelf was dominated by intrazonal communities such as halophyte grasslands and freshwater wetlands instead of zonal steppe or semi-arid desert.All above evidence demonstrated that the fundamental changes of pollen assemblage and their origins in Okinawa Trough since~200 ka BP were affected by combine factors including the coastline position and climate fluctuation.Moreover,the substantial shortening of distance between shoreline and the Okinawa Trough driven by orbital insolation cycles was clearly indicated by the pollen spectra,whereas the source-area climate signal of the pollen record was largely weakened.     

Palynological record during the Pleistocene (between 1.05 Ma and 0.36 Ma) from ODP1144, northern South China Sea

This paper presents the pollen record from the lower section of ODP1144 (depth 501.3-225.7 m, ca. 1.05-0.36 Ma). Two pollen zones (PA and PB) and eleven pollen subzones are recognized. Within zone PB, the 11 pollen subzones (PB21-11) are defined according to the pine, fern and herb variations, and are equivalent to the marine isotope stages 21-11 (MISs 21-11). The interglacial periods are typified by an increase in pine pollen and fern spores, and a decrease in herbaceous pollen, while the patterning during the glacial periods is just the opposite. During the interglacial periods, pollen assemblages were dominated by pine similar to those of the present day, suggesting that the paleoenvironment of the interglacial periods was similar to that of the present day, whereas the glacial periods are marked by an increase in herbaceous pollen, mainly Gramineae and Cyperaceae, indicating that grassland covered the exposed continental shelf when sea level declined. Increased Artemisia percentages and the highest     

Quantitative relationship between pollen and vegetation in northern China

205 surface pollen samples from different communities in Northern China were analyzed to understand the quantitative relationship between pollen and its original vegetation. Pollen analysis and vegetation investigation show that the pollen assemblages differ a lot in different vegetation regions. Arboreal pollen account for more than 30% in temperate broad-deciduous forests region. In temperate steppe regions, herb pollen percentages are more than 90%, where Artemisia and Chenopodiaceae are domi- nant pollen types with Artemisia percentages more than 30%. In temperate desert, Chenopodiaceae pollen percentages are more than Artemisia, where ferns are rare. Cyperaceae pollen percentages are more than 20% in sub-alpine or cold meadows. The relations between pollen percentages and vegeta- tion cover indicate that most arboreal pollen shows a close relationship with parent plant covers, most shrubby pollen types have more or less correlations, but most herbs do not show clear correlations. For arboreal pollen types, Picea pollen shows the closest correlation with spruce trees coverage, then is Quercus and Carpinus. Betula, Larix and Juglans have also high correlation coefficients with their plants coverage, but Betula pollen is of overrepresented pollen type and more than 40% in birch forest, while Larix and Juglans pollen is underrepresented and pollen percentages are more than 10% in Larix or Juglans pure forests. Pinus is of overrepresented pollen type, and pollen percentages have some relations with plants cover. Pine forest might present when Pinus pollen percentages are more than 30%. The relations between Ulmus and Populus pollen percentages and vegetation cover are not close, where they are mixed with other arbors, they cannot be recorded easily, but if their pollen percentages are more than 1%, Ulmus or Populus trees should exist. For shrubby pollen types, the correlation be- tween Vitex pollen percentages and vegetation cover is the highest, then is Corylus, Tamariaceae and Nitraria, and their pollen percentages are less than 1% where original plant are absent. Caragana and Spiraea pollen percentages have some relations with vegetation cover. The relations between pollen percentages and vegetation cover are not clear for Rosaceae and Saxifragaceae. For herb pollen types, Cyperaceae pollen has the closest correlation with vegetation cover, where pollen percentages are more than 20% when Cyperaceae are constructive or dominant species in vegetation, and pollen per- centages are less than 5% where Cyperaceae are not constructive or dominant species (cover less than 30%). Artemisia and Chenopodiaceae pollen percentages mainly have close relations with ecological regions. The relations between pollen percentages and cover are not clear for Gramineae, Legumi- nosae and Compositae.     

富蕴水磨沟探槽的孢粉组合特征及其意义

本文应用孢粉分析对富蕴水磨沟探槽的地层年代和古环境进行了探讨,认为富蕴地区在新冰期第一期活动中气候干净,为寒冻荒漠植被;在大西洋期为暖干气候,生长了草原化荒漠植被;在其后的新冰期活动中为冷湿气候,发育了灌丛草原植被。结合新疆特殊的地理条件,将上述环境演变过程与国内外全新世气候波动研究结果相比较,并参考有关(14)~C数据,作者认为该探槽中发现的第一次古地震活动应晚于6000a,B.P,第二次古地震活动似应发生于2500a,B.P之后。     

Characteristics of the modern pollen assemblages from different vegetation zones in Northeast China: Implications for pollen-based climate reconstruction

Northeast China is an essential area for studying the strength of East Asian Summer Monsoon(EASM), due to its northernmost location in EASM domain. However, the lack of sufficient modern pollen data in this region hinders an effective interpretation of fossil pollen records and quantitative vegetation/climate reconstructions. Here, 44 surface pollen samples from forest, steppe, and meadow were used to explore pollen-vegetation-climate relationships. Cluster analysis, species indicator analysis, and principal components analysis, were used to identify the discontinuous and continuous trends in pollen dataset. In addition, correlation analysis and boosted regression trees were used to investigate primary explanatory variables, while coinertia analysis and redundancy analysis to examine pollen-vegetation and pollen-climate correlations respectively. Our results show that:(1) vegetation can be well represented by surface pollen assemblages, i.e. forest is characterized by a high proportion of tree pollen(70%) dominated by Betula(40%) along with Alnus, Larix, and Pinus, whereas Steppe by herb pollen(80%),dominated by Artemisia, Chenopodiaceae;(2) significant correlations exist between pollen assemblages and mean annual temperature and then mean annual precipitation;(3) pollen ratios of Artemisia/Chenopodiaceae and arboreal/non-arboreal can respectively be used as good indicators of humidity and temperature in Northeast China.